Welcome to the club. If your getting LT's you will need a tune as you will get error codes. The reason for the code is because the second sensor is further away than original and a extension is needed.

Lean is what you don't want to be running (AFR's between 13.5 and up) as this can cause detonation and cause the pistons and rings to go bad leading to a blown engine over time. Also will cause fuel to get into your oil pan. Running rich is not good just because your burning more fuel than your suppose to, but not bad.

well I guess that will have to be put off for a few years till I get more of the warranty used up.